Raney alloy methanation catalyst

ABSTRACT

A methanation process utilizing an improved catalyst for the conversion of CO, CO 2  and mixtures thereof to CH 4  is disclosed. The catalyst comprises a monolithic mesh type structure of a nickel alloy having an integral Beta phase Raney coating on its outer surfaces. When used, substantially higher reactant flow rates and lower operating temperatures are possible as compared to conventional fluidized bed granular catalysts.

This is a division, of application Ser. No. 353,534, filed Mar. 1, 1982.

FIELD OF THE INVENTION

The present invention is an improved catalyst for use in a process andapparatus for the production of methane from gases containing carbonmonoxide, carbon dioxide or mixtures thereof and hydrogen.

BACKGROUND OF THE INVENTION

"Methanation" is a catalytic reaction which yields methane gas fromcarbon monoxide, carbon dioxide or mixtures thereof and hydrogenaccording to the equations:

    CO+3H.sub.2 =CH.sub.4 +H.sub.2 O, ΔH=-52.7 Cal       (1)

    CO.sub.2 +4H.sub.2 =CH.sub.4 +2H.sub.2 O, ΔH=-43.6 Cal (2)

The limited availability of methane from natural sources coupled withthe enormous utility of methane as a clean, sulfur free fuel havecombined to create a great need for "synthetic natural gas". Methanemade by methanation holds great economic significance because thereactants can be obtained by a reaction involving readily available coalwith steam according to the basic equations:

    2C+2H.sub.2 O=2CO+2H.sub.2                                 ( 3)

and

    CO+H.sub.2 O=CO.sub.2 +H.sub.2                             ( 4)

to produce

    2C+3H.sub.2 O=CO.sub.2 +CO+3H.sub.2                        ( 5)

Reactions (1) and (2) are highly exothermic and are reversible so thathigh temperatures tend to reduce the yield of methane. Accordingly, heatremoval poses a significant problem in all methanation processes. Inaddition, many of the processes either do not convert carbon dioxide tomethane or are sensitive to the presence of sulfur compounds and/or anexcessive amount of water in the process gases.

Conventional prior art methanation processes are conducted by usuallypassing the gaseous reactants through a packed or fluidized bed of acatalyst which is typically nickel or a nickel alloy with platinum. Sucha process is disclosed, for example, in U.S. Pat. No. 3,930,812 issuedto Harris et al. However, packed bed processes such as that of Harris etal are characterized by temperature control problems and a largepressure drop across the reactor. Dorschner et al, in U.S. Pat. No.2,662,911, conduct the reaction in a plurality of catalyst packed tubesvertically arranged in a water-containing drum. Dorschner, in U.S. Pat.No. 2,740,803, also discloses methanation in a fluidized bed providedwith double-wall bayonette type heat exchangers. This latter Dorschnerpatent also discloses an embodiment wherein the catalyst is contained in"contact tubes, vertically arranged in a water-containing drum havingdiameters which progressively decrease from the top to the bottom".These methods, like the more conventional packed bed methods, are alsocharacterized by high pressure drops across the reactor.

Further, in most, if not all, of the foregoing prior art methanationprocesses characterized by the use of granular or particulate catalysts,there is a .[.tendancy.]. .Iadd.tendency .Iaddend.to form coke on theirsurfaces and plug up over prolonged periods of time.

Lastly, it is known to use Raney nickel as a catalyst in methanationprocesses. See, for example, "Methanation Studies on Nickel-AluminumFlame Sprayed Catalysts" by Baird and Steffgen, Journal of IndustrialEngineering Chemistry, Product Research Development, Volume 16 No..Iadd.2 .Iaddend.(1977), in which the use of a methanation catalystprepared by flame spraying aluminum onto a nickel surface followed byheating to form a Raney-type alloy and then activating it with a causticleach is discussed. In this article, it was found that there was astrong correlation between the NiAl₃ (beta nickel) content in theunleached alloy and the methanation activity of the leached catalyst. Nomention of the use of molybdenum, titanium, tantalum or ruthenium asalloying ingredients of the nickel is given or suggested.

Additional studies involving nickel-molybdenum methanation catalystswere reported by Wilhelm, Tsigdinos and Fernece, "Preparation andActivity of Nickel-Molybdenum Methanation Catalysts"; Chemical Uses ofMolybdenum Proceedings, 3rd International Conference (1979). However, nomention of Raney treatment is given or suggested. When these catalystswere used even at elevated temperatures and pressures, useful COconversions were reported to be in the neighborhood of only 80 to 90percent. No suggestion of applicability to CO₂ is given.

Most recently, U.S. Pat. No. 4,043,946 issued to Sanker et al disclosesa method for making a supported Raney nickel catalyst containing up to 5percent molybdenum which, when tested for methanation activity, wasfound to require a temperature on the order of 320° C. to achieve a COconversion of about 99 percent. No mention is made of potentialapplicability to CO₂.

SUMMARY OF THE INVENTION

The present invention provides an improved monolithic Raney methanationcatalyst for use in a high velocity methanation reaction whereinhydrogen is reacted with a carbon-bearing oxide selected from the groupconsisting of CO, CO₂ and mixtures .[.therof.]. .Iadd.thereof.Iaddend.to form methane, said catalyst being of the type comprised ofan integral Raney metal surface layer on a suitable substrate whereinsaid surface is predominantly derived from an adherent Beta structuredcrystalline precursory outer portion of said substrate.

Another embodiment of the invention is provided by the use of amonolithic Raney methanation catalyst of the type that comprises anintegral Raney metal surface layer on a metallic mesh substrate, saidRaney .[.meta.]. .Iadd.metal .Iaddend.surface layer being predominantlyderived from an adherent Ni_(x) M_(1-x) Al₃ Beta structured crystallineprecursory surface layer, where M is a catalytic enhancer taken from agroup consisting of the metals, molybdenum, titanium, tantalum.Iadd.,.Iaddend..[.and.]. ruthenium.Iadd., and mixtures thereof .Iaddend.and x,the weight fraction of nickel in the combined NiM alloy, is within therange of from about 0.80 to about 0.95.

The invention further comprises a method of using a Raney catalyst in amethanation reaction wherein said catalyst is produced by

(a) coating with aluminum, the surfaces of a clean, non-porousperforated metal base structure of an alloy comprising from about 5 toabout 20 percent by weight of a stabilizing metal selected from thegroup consisting of molybdenum, titanium, tantalum, or ruthenium, andfrom about 80 to about 95 percent by weight of nickel;

(b) heating said coated surfaces by maintaining said surfaces at atemperature of from about 660° C. to about 750° C. for a time sufficientto infuse a portion of said aluminum into outer portions of saidstructure to produce an integral alloy layer of nickel, the stabilizingmetal and aluminum in said outer portions predominantly of Betastructured grains, but insufficient in time to create a predominance ofGamma structured grains in said outer portions; and

(c) leaching out residual aluminum and intermetallics from the alloylayer until a Raney nickel alloy layer is formed integral with saidstructure.

These and other objects of the subject invention will become apparentfrom the following description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of a process for the preparation of an expandedmesh embodiment of the catalyst as used in the present invention.

FIG. 2 shows the overall appearance of an expanded mesh embodiment ofthe catalyst of FIG. 1 after NaOH leaching.

FIG. 3 is a 250× photomicrograph of a section of the mesh embodiment ofthe catalyst of FIG. 2 showing a Raney Ni-Mo layer after heat treatmentand leaching.

FIG. 4 is a 750× enlargement of a section of the Raney coating of FIG.3.

FIG. 5 is a vertical cross section through an exemplary methanation cellin which the catalyst of the present invention may be used.

FIG. 6 is a 150× photomicrograph of the catalyst of FIG. 2 as itappeared after 307 hours use showing the Raney coating still largelyintact with substantially no coke formation on the coating.

FIG. 7 is a 750× enlargement of a section of the Raney coating of FIG.6.

FIG. 8 is a comparison of the response of an Ni-Mo catalyst according tothe present invention with the effectiveness of a commercially availableAl₂ O₃ supported, molybdenum promoted granular Raney nickel catalyst forthe methanation of CO.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

This invention is described in terms of the preparation and use of anickel alloy catalyst having about 5 to about 20 percent molybdenumtherein. It should be understood that the molybdenum may be replaced inwhole or in part by ruthenium, titanium or tantalum in the broaderaspects of the invention.

Catalyst Preparation

Catalyst (5) of the present invention is prepared as shown in FIG. 1.The integral Raney nickel alloy surface of the monolithic catalyst (5)of this invention is formed on a supportive nickel bearing core orsubstrate. While cores of substantially pure nickel or an appropriatenickel bearing alloy such as Inconel 600, Hastelloy C or 310 stainlesssteel can be used, it is preferred to have the outer portions of thecore (core is used interchangeably herein with substrate) itself serveas the nickel bearing alloy outer layer. Where cores of other materialsor alloys are used, a nickel alloy coating of the desired compositionshould first be deposited onto the surfaces thereof by a variety ofknown techniques such as metal dipping, electroplating, electrolessplating and the like. This coating should be at least 100 microns andpreferably at least 150 microns thick. This helps to substantiallyimprove the thermal stability of the coating by making the transitionacross the coating/substrate interface much less abrupt and thus greatlyreducing tensile stresses and the possibility of corrosion andsubsequent failure at this interface.

Accordingly, the core material for the catalyst of the present inventioncomprises an alloy in which nickel and the selected alloying materialare melted together to form a precursor ingot (10) having the desiredcomposition. When the alloying metal is molybdenum, the preferred weightpercentage is between about 10 and about 18; for ruthenium, it isbetween about 5 and about 10 percent; for tantalum, it is between about5 and about 15 percent and for titanium, it is between about 5 and about10 percent. Thus it can be seen that in the preferred embodiments of theinvention in the formula Ni_(x) M_(1-x) Al₃,

x is between about 0.82 and about 0.90 when M is molybdenum;

x is between about 0.90 and about 0.95 when M is ruthenium;

x is between about 0.85 and about 0.95 when M is tantalum; and

x is between about 0.90 and about 0.95 when M is titanium. The castingot is then rolled out to form a sheet or strip (12) preferably in thethickness range of between about 0.01 and about 0.02 inch.

While support for the catalyst of the current invention can be in theform of any conveniently shaped structure, a perforated metal base,particularly an expanded metal screen or mesh (14), is preferred. Suchan open structure is found to be a significant factor in providing acatalytic process having substantial life-time and operationaladvantages over other types of catalytic structures used for thispurpose. The final mesh which is prepared by conventional metalexpansion techniques forms a regularly shaped diamond or square celledstructure typically having cells on the order of 0.2 to 0.3 inch on aside. The thickness and mesh opening values are not critical and,depending on such factors as alloy composition and reaction parameters,other cell sizes could easily be used.

Prior to further processing, expanded mesh (14) is thoroughly cleaned byconventional means, such as degreasing, acid etching and/or gritblasting (16) to remove surface .[.contaminates.]. .Iadd.contaminants.Iaddend.and thus improve the wetting of the subsequently appliedaluminum to the surface.

Formation of the catalyst begins when this clean surface is subjected toan aluminizing treatment (18). By "aluminizing", as used herein, it ismeant that aluminum is brought into intimate contact with the cleanednickel bearing alloy material at the surface of the core so that whenheat-treated at interdiffusion step (20), the desired nickelalloy-aluminum alloy layer is formed. This can be accomplished by any ofseveral known methods such as flame or plasma spraying the aluminum ontothe surface of the core, dipping the core into molten aluminum or by theuse of fused salt electrolysis, with dipping being preferred.

Whichever method of aluminizing is used, an aluminum layer of at least100-micron thickness should be deposited on the surface of the core.Much thicker aluminum layers of, for example, greater than 500-micronthickness, perform .[.satisfactory.]. .Iadd.satisfactorily .Iaddend.inthe process but for reasons for economy, aluminum layer thicknesses ofbetween about 150 and about 300 microns are preferred. With dipping,such a thickness is achieved in a time of between about 0.5 and about5.0 minutes when the aluminum is between about 600° C. and about 700° C.

Interdiffusion step (20) is carried out at a temperature of at least660° C., i.e., above the normal melting point of aluminum. However, todrive the interdiffusion process at a reasonable rate, highertemperatures should be used, with the temperature within the range offrom about 700° C. to about 750° C. and particularly from about 715° C.to about 735° C. being most preferred. Usually, interdiffusion iscarried out in an atmosphere of hydrogen, nitrogen or an inert gas toprevent oxidation of the surface. This interdiffusion heat treatment iscontinued for a time sufficient for the aluminum and nickel alloy toreact to form a nickel alloy-aluminum ternary alloy of at least 40microns and preferably at least 80 microns in thickness. Interdiffusiontimes within the range of from about 5 to about 30 minutes satisfy thisneed. For nickel-molybdenum, interdiffused alloy layers of about 100 toabout 400 microns in thickness are preferred, with best results obtainedat between from about 150 to about 300 microns.

During heat treatment at temperatures above 660° C. excessively longinterdiffusion times, e.g. 1 hour or more, and excessively hightemperatures, should be avoided for technical as well as economicreasons. Thus, at temperatures above about 855° C., the Beta phasequickly transforms into liquid and Gamma phase. Further, ifinterdiffusion at any temperature is continued too long, all of theavailable aluminum can be diffused into the nickel resulting in a largeexcess of nickel in the interdiffused layer. Under these circumstances,especially at interdiffusion temperatures of much above about 800° C.,an intermetallic NiAl (Eta) phase forms which is quite resistant tosubsequent leaching of the aluminum so that a Raney nickel alloy surfacewill not form.

Lastly, for coatings on a substrate differing in composition from thecoating, extended heat treatments might damage the substrate or formundesirable brittle intermetallics at the coating substrate interface.For example, if aluminum is diffused into a nickel alloy coated steelcore, excessive interdiffusion time or temperature can result in thealuminum "breaking through" to diffuse into the steel base of the core.This results in the formation of a very brittle FeAl₃ intermetallicphase which will significantly undermine the strength of the bondbetween the core and the interdiffused layer.

By providing sufficient quantities of aluminum and nickel, whileavoiding excessively long treatments or excessively high temperaturesduring interdiffusion, breakthrough and formation of the undesiredintermetallics are avoided.

The formation of the desired nickel-molybdenum-aluminum Beta structuredternary alloy layer is followed by a selective leaching step (22),wherein sufficient aluminum is removed to form an active nickel alloysurface layer. For this a strong aqueous base, such as NaOH, KOH orother strongly basic solution capable of dissolving aluminum, isgenerally used. Preferably, leaching is carried out with an aqueouscaustic solution containing about 1 to about 30 weight percent NaOH. Apreferred selective leaching procedure for producing porous nickelsurfaces of the invention is carried out first for 2 hours with 1percent NaOH, then for 20 hours with 10 percent NaOH, both of thesesubsteps being under ambient conditions in which temperature is notcontrolled, and finally for 4 hours with 30 percent NaOH at 100° C. Thisleaching procedure removes at least about 60 percent and, preferablybetween about 75 to about 95 percent, of the aluminum from theinterdiffused alloy layer and as shown in FIGS. 3 and 4 provides aporous nickel surface of unusually high catalytic activity. It isrecognized that the leaching conditions can be varied from thosementioned above to achieve equally effective selective dissolution ofthe aluminum.

The appearance of mesh (14) at this stage is shown in FIG. 2. Anenlarged cross section (250×) of a strand of treated Ni-12Mo expandedmetal is shown in FIG. 3 and a 750× enlargement of the porous Raneysurface coating is shown in FIG. 4. In these, it is seen that the Betastructured Raney Ni-12Mo layer is about three times as thick as theunderlying Gamma layer. Since the predominant Beta layer is the outerlayer which will be in contact with any medium in which the coated coreis placed and is what serves to control the catalytic activity of thecoating, the structure shown in FIGS. 3 and 4 is collectively called aBeta Raney Ni-12Mo coating.

After the selective leaching, the active nickel alloy coatings mayexhibit a tendency to heat up when exposed to air. If uncontrolled, thisself-heating or pyrophoric tendency can easily lead to problems withcoating ignition with consequent severe damage to the coating. However,chemically treating (24) the porous nickel alloy layer has been found toeliminate this problem. Convenient methods for this chemical treatmentinclude immersing the porous nickel alloy for between at least 1 hourand 4 hours in a dilute aqueous solution of an oxidant containing, forexample, by weight either

(a) 3 percent NaNO₃, or

(b) 3 percent K₂ Cr₂ O₇, or

(c) 3 percent NaClO₃ and 10 percent NaOH, or

(d) 3 percent H₂ O₂.

This treatment safely eliminates the self-heating tendency of the porousnickel alloy surface without diminishing either its catalytic activityor mechanical properties.

.[.Although the active porous nickel alloy surface layers, as preparedby the proceeding steps, have satisfactory mechanical properties and alow tendency to crack, compared with many of the Raney nickel surfacesof the prior art, the mechanical properties of the layer can be improvedstill further by optionally coating a very thin layer of nickel onto theporous surface (26). This nickel layer, which is preferably 5 to 10microns thick, can be applied from conventional electroless nickel or anickel electroplating bath and enhances the mechanical strength of theporous nickel alloy layer without diminishing its catalytic activity..].

Methanation Studies

Referring now to FIG. 5, an exemplary methanation reactor (100) is shownin a cross-section in which a catalyst of this subject invention can beused. As shown, it comprises at least one reaction chamber (112) intowhich a plurality of layers (114) of catalyst (5) are loosely stacked,said layers being arranged so that the open structure of the meshsubstrate is randomly oriented. A scrubbed mixture of hydrogen, and agaseous carbon-bearing material such as carbon monoxide, carbon dioxideor a mixture thereof is admitted to the interior of reactor (100)through gas inlet (116). To insure that the reaction is driven tocompletion, a relatively large excess of hydrogen is normally used,typically being in the range of between about 3 to about 9 parts of H₂per part of carbon-bearing material. The entering gas mixture passesthrough annulus (117) which is between discharge tube (118) and innerjacket (120) to enter the top of reaction chamber (112) and passtherethrough, contacting catalyst (5) and reacting enroute. The openstructure presents a relatively low impedance to the gas so that theobserved pressure drop through the reactor is quite small. This lowpressure drop combined with the high reactivity of the catalyst allowsextremely high gas-flow rates through the system.

The reaction products pass first through porous filter (122) in thebottom of reaction chamber (112) to remove any solid particles presentand then leave the reactor through discharge tube (118) and gas outlet(124). Such an arrangement allows the incoming gas to be heated whilethe reaction products are cooled to prevent reversing the reaction ofequations (1) and (2), supra. The overall reactor system is surroundedby an outer pressure jacket (126) which is sealingly mated with coupling(128) to hold the parts in alignment and keep the system pressure tight.Temperatures within the reactor are measured by thermocouple (130).After the gases pass out of reaction chamber (112), they are fed into arecovery system (not shown) wherein the methane and any other higherhydrocarbons formed are separated and recovered from the reactants.Unreacted materials, mostly hydogen, may be recycled back into thereactor as fresh feedstock.

The catalyst of the present invention is readily adaptable to gassystems containing mixtures of hydrogen with either CO, CO₂ or a mixturethereof so that a wide range of starting materials can be used. Forexample, the carbon oxide starting material can be derived from thecontrolled combustion of coal or similar materials in either speciallydesigned reactors or from the scrubbed smoke stack effluents from powerstations, steam generators and similar carbon based fuel-burningapplications. Hydrogen can be derived either from the electrolysis ofwater or conveniently obtained from the output of electrolyticchlor-alkali cells which typically give off large quantities of hydrogenas a by-product.

As shown, reactor (100) does not have an inherent or self-heatingcapability to start the reaction. Rather, it is adapted to have externalheating means, such as a furnace (not shown), placed around it so as toprovide a controlled source of heat to the gases flowing in annulus(117) and to allow overall temperature of the system to be slowly raiseduntil the gases start to react in reaction chamber (112). This usuallyhappens at between 150° C. and 170° C. In large applications, thistemperature could be reached by preheating the incoming gases prior totheir entering the system. However, this temperature is achieved, thehighly exothermic nature of the reaction usually supplies sufficientadditional heat to quickly raise the system temperature to a point whereessentially all of the carbon-bearing material in the heated gas streamis converted to methane, ethane and higher hydrocarbons. For the systemshown, in an operating range of about 250° C. to about 270° C., it isfound that the conversion of the carbon oxide material to methane isessentially complete with only minimal amounts of ethane and higherhydrocarbons being produced.

The reaction temperature of 250°-270° C. is substantially lower than isnormally utilized for systems of this type. Further, when applied withan overall system pressure of between about 50 and about 100 p.s.i.,reaction of the carbon-bearing materials to form methane isexceptionally high. These pressure values are also substantially lowerthan normally utilized for systems of this type.

Operating at such a low pressure is highly advantageous since it permitsa considerable economy in the design of a full-sized system formethanation as described herein. It has been found, however, that highersystem pressures seem to promote the production of significantquantities of ethane and higher hydrocarbons in the reaction mass. Sucha situation would appear to allow considerable flexibility in the natureof the final product or products produced.

Utilizing the apparatus of FIG. 5, an equilibrium or isothermalcondition was quickly established which was sustained, withoutdifficulty, for as long as 36 hours without a need to internally coolthe reacting gases. It was further found that the problems noted in theprior art in stabilizing the reactor to prevent either the formation ofcoke and consequent plugging of the catalyst surface or the reverse didnot occur. This is because the extremely high rate of gas-flow throughthe catalyst and the heat sinking of the relatively high percentage ofexcess hydrogen set up conditions wherein the reaction is essentiallyself-quenching once it passes through the catalyst stack.

FIG. 6 is a photograph of a 150× enlargement of a strand of the catalystof the present invention after 307 hours of use in the methanationreactfor of FIG. 5. FIG. 6 shows that the surface is substantially freeof carbon and that the overall thickness of the strand has not beenmaterially reduced from its thickness prior to use. These effects aremore clearly shown in FIG. 7 which is a photograph of a 750×magnification of the coating of FIG. 6.

One problem frequently encountered with many catalysts is their highsensitivity to sulfur contamination in either the form of H₂ S or SO₂ inthe inlet gases. In commercial Raney nickel catalysts, tolerance valuesas low as 0.1 part per million are frequently found. The catalyst ofthis invention operates in the presence of a substantially higher valueof sulfur in either form as compared to commercial catalysts now in usewithout poisoning the catalyst for continued use.

The following examples are given to illustrate the invention and are notdeemed to be limiting thereof. All parts and percentages are by weightunless otherwise specified.

EXAMPLE 1

A catalyst was prepared as follows:

One inch diameter discs of about 0.015 inch thick Ni-12Mo alloy whichhad been expanded to a mesh having a diamond cell structure withdimensions of about 0.2 inch by 0.3 inch on a side was thoroughlycleaned by degreasing with acetone, lightly etching with 10 percent HCl,rinsing with water and, after drying, grit-blasting with No. 24 grit Al₂O₃ at a pressure of 3.4 kg/CM² (50 p.s.i.).

The cleaned nickel aluminum alloy discs were aluminized by applying acommercial flux and then dipping in a pot of molten aluminum at 675° for1 minute to entirely coat the discs with aluminum. The aluminized discswere then heat-treated at 725° for 15 minutes in a nitrogen atmosphereto interdiffuse the nickel alloy and aluminum. After heat-treating, thediscs were allowed to cool in a current of nitrogen for about 2 hourswhich produced a predominantly Beta phase structured, interdiffusedlayer on the surface.

The discs were then subjected to a leaching treatment in which thealuminum was selectively removed from the interdiffused layer to form anactive porous nickel-molybdenum surface on the discs. The leachingtreatment consisted of immersing the interdiffused discs in 20 percentNaOH at 80° C. for approximately 1 hour to dissolve away the excessaluminum and expose the catalytically active Beta phase. After leaching,the catalyst discs were first washed to remove loose material and thenplaced in the reactor of FIG. 5 while still wet and dried in a stream ofhydrogen. They were then activated by continuing the flow of hydrogen ata temperature of about 300° C. for about 16 hours.

EXAMPLE 2

Using the catalyst of Example 1 and the reactor of FIG. 4, a disc stackheight of about 2 inches having a total catalyst content of about 12grams and solid volume of about 1.6 cc was assembled in reaction chamber(112). An 8:1 mixture of hydrogen and CO at a pressure of 180 p.s.i. wasadmitted at a flow rate of about 1350 cc per minute. This produced aspace velocity of about 50,625 hours⁻¹ or about 6,750 cc per gram-hour.

Starting at a room temperature, the temperature of the reactor wasgradually raised with samples being periodically taken to monitor theprogress of the reaction. The results obtained are given in Table I.They show that the reaction began at a temperature of about 200° C. andthat at a temperature of about 265° to 270° CO to hydrocarbon conversionwas approaching 100 percent. The reactor was run in an isothermal modefor another 4 to 6 hours after which the reaction was terminated.Analyses of the output gases showed that above 265° C. the conversion ofCO was essentially complete with about 95 percent going into CH₄ andabout 5 percent going into C₂ H₆ and "other" products which wereunidentified. At a temperature of about 350° C., only CH₄ was produced.Examination of the catalyst showed essentially no carbon buildup orother source of degradation.

                  TABLE I                                                         ______________________________________                                                          % YIELD                                                     TEMP (C.)*                                                                             % CONVERSION   CH.sub.4                                                                             C.sub.2 H.sub.6                                                                     "OTHER"                                  ______________________________________                                        140      0              0      0     0                                        170      0.08           0.08   0     0                                        190      0.92           0.92   0     0                                        200      6.62           3.31   1.65  1.66                                     210      19.32          11.47  3.93  3.92                                     230      25.04          14.76  5.14  5.14                                     265      98.91          94.18  2.36  3.37                                     300      99.54          94.63  2.46  2.45                                     330      99.58          94.61  2.48  2.49                                     350      99.54          99.54  0     0                                        ______________________________________                                         *Pressure 180 p.s.i.                                                     

EXAMPLE 3

The method of Example 2 was repeated with the H₂ :CO ratio beingdecreased to a value of 4:1. The results obtained with this higher COconcentration were substantially the same as those of Example 2.

EXAMPLE 4

The method of Example 2 was repeated except that the reactor pressurewas 50 p.s.i. While the 100 percent reaction temperature of 270° C. wassubstantially the same as with higher pressure operation, analyses ofthe output gases showed that all of the CO was converted to CH₄ with notraces of C₂ H₆ or other hydrocarbons being observed. Results of thisrun are given in Table II.

                  TABLE II                                                        ______________________________________                                                          % YIELD                                                     TEMP (C.)*                                                                             % CONVERSION   CH.sub.4                                                                             C.sub.2 H.sub.6                                                                     "OTHER"                                  ______________________________________                                        160      0              0      0     0                                        180      0.18           0.18   0     0                                        200      0.99           0.99   0     0                                        210      2.31           2.31   0     0                                        220      3.55           3.55   0     0                                        230      7.79           7.79   0     0                                        245      15.51          15.51  0     0                                        260      97.46          97.46  0     0                                        265      99.19          99.19  0     0                                        270      99.23          99.23  0     0                                        ______________________________________                                         *Pressure 50 p.s.i.                                                      

EXAMPLE 5

The method of Example 2 was repeated with the CO being replaced by CO₂.The results obtained were substantially the same as those in Example 2.

EXAMPLE 6

The method of Example 2 was repeated with the incoming gas being amixture of H₂, CO and CO₂ in a ratio of about 8:1:1. It was found thatthe conversion of both gases was nearly 100 percent at 260° C. to 270°C. with substantially all of the reaction product being CH₄. The resultsobtained are illustrated in FIG. 8.

Comparative Example A

Using a commercial granular Al₂ O₃ supported Raney Ni-Mo catalyst(Davision 3000) and the reactor of FIG. 5, 4.9678 grams of catalysthaving a total volume of 8.998 cc were placed in the reaction chamber.An 8:1 mixture of H₂ and CO at a reactor pressure of 100 p.s.i.g. wasadmitted at a flow rate of 758.3 cc per minute. This produced a spacevelocity of about 50564.57 hours⁻¹ or about 9158.58 cc per gram-hour.

The method of Example 2 was then repeated with the results shown inTable III and FIG. 8. The reaction initiated about 190° and did notachieve substantially complete CO conversion until a temperature inexcess 325° C. was obtained. The results of Example 6 are plotted withthese data to provide a more direct comparison with the catalyst of thisinvention.

                  TABLE III                                                       ______________________________________                                                          % YIELD                                                     TEMP (C.)*                                                                              % CONVERSION  CH.sub.4 C.sub.2 H.sub.6                                                                    C.sub.3 H.sub.8                         ______________________________________                                        155       0             0        0    0                                       175       0.45          0.45     0    0                                       185       1.05          1.05     0    0                                       200       5.54          5.54     0    0                                       210       5.63          5.63     0    0                                       325       99.3          99.3     0    0                                       345       99.48         99.48    0    0                                       360       99.5          99.5     0    0                                       ______________________________________                                         *Pressure 100 p.s.i.                                                     

EXAMPLE 7

Using the method of Example 1, a Raney mesh catalyst having 5 percent Ruwas fabricated. This was assembled in the reactor of FIG. 5 and themethod of Example 2 repeated with a reactor pressure of 100 p.s.i.Analyses of the output gases .[.as.]. .Iadd.is .Iaddend.shown in TableIV. The reaction was initiated at a temperature of about 200° C. with asubstantially 100 percent conversion of the CO at a temperature of 338°C. At temperatures above about 215° C., ethane is produced and attemperatures above 260° C., propane is produced.

                  TABLE IV                                                        ______________________________________                                               %          % YIELD                                                     TEMP (C.)*                                                                             CONVERSION   CH.sub.4                                                                             C.sub.2 H.sub.6                                                                    C.sub.3 H.sub.8                                                                    "OTHER"                                ______________________________________                                        170      0            0      0    0    0                                      200      0.56         0.56   0    0    0                                      215      2.03         1.4    0.31 0    0.32                                   225      4.75         3.45   0.65 0    0.65                                   235      7.37         5.46   0.96 0    0.95                                   245      11.64        8.46   1.59 0    1.59                                   260      26.17        19.1   3.4  0.09 3.58                                   300      88.33        78.45  2.22 1.81 5.85                                   320      91.84        82.96  1.62 1.88 5.38                                   338      99.72        94.53  0.25 1.57 3.37                                   ______________________________________                                         *Pressure 100 p.s.i.                                                     

EXAMPLE 8

The method of Example 7 was repeated with CO₂ and reactor pressures of100 and 200 p.s.i. with the results shown in Tables V and VI,respectively. It is interesting to note that although highertemperatures were used, no traces of ethane or propane were observed ineither run when CO₂ was the starting gas.

                  TABLE V                                                         ______________________________________                                                          % YIELD                                                     TEMP (C.)*                                                                              % CONVERSION  CH.sub.4 C.sub.2 H.sub.6                                                                    C.sub.3 H.sub.8                         ______________________________________                                        225       0.68          0.68     0    0                                       245       1.43          1.43     0    0                                       255       2.98          2.98     0    0                                       275       4.4           4.4      0    0                                       310       14.1          14.1     0    0                                       365       63.12         63.12    0    0                                       390       75.34         75.34    0    0                                       420       84.74         84.74    0    0                                       440       90.54         90.54    0    0                                       475       96.45         96.45    0    0                                       ______________________________________                                         *Pressure 100 p.s.i.                                                     

                  TABLE VI                                                        ______________________________________                                                          % YIELD                                                     TEMP (C.)*                                                                              % CONVERSION  CH.sub.4 C.sub.2 H.sub.6                                                                    C.sub.3 H.sub.8                         ______________________________________                                        235       1.21          1.21     0    0                                       250       2.59          2.59     0    0                                       275       5.9           5.9      0    0                                       310       15.5          15.5     0    0                                       350       47.24         47.24    0    0                                       390       77.99         77.99    0    0                                       395       77.71         77.71    0    0                                       415       86.01         86.01    0    0                                       435       91.79         91.79    0    0                                       460       99.48         99.48    0    0                                       ______________________________________                                         *Pressure 200 p.s.i.                                                     

EXAMPLE 9

The method of Example 2 was repeated with the incoming gas beingcontaminated by 24 parts per million of H₂ S. After a temperature of200° C. was reached, the reaction was continued at that temperatureuntil a total run-length of 27 hours was achieved, during which timesome 4.7×10⁷ ppm sulfur passed over the catalyst. Analyses of the outputgas showed no decrease in the activity of the catalyst or change in thecomposition of the reaction products.

EXAMPLE 10

The method of Example 2 was repeated with a contamination of 500 partsper million of SO₂ being added to the input gas. After a temperature ofabout 200° C. was reached, the reaction was continued at thattemperature until a total run-length of 49 hours was achieved, duringwhich time a total of 1.7×10⁹ ppm sulfur passed over the catalyst.Analyses of the output gases showed a gradual reduction in conversionrate reaching a value of about 40 percent by the end of the run butessentially no change in the composition of the reaction products.

This invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed is: .[.1. A monolithic catalyst comprised of a metallic substrate with an integral Raney metal exterior surface, said surface being predominantly derived from an adherent Ni_(x) M_(1-x) Al₃ Beta structured crystalline precursory layer, where said layer is integral with and derived from said substrate, M is a catalytic enhancer selected from the group consisting of molybdenum, titanium, tantalum, ruthenium or mixtures thereof and where x, the weight fraction of nickel in the combined weight of Ni and M, is within the range of from about 0.80 to about 0.95..]. .[.2. The catalyst of claim 1 wherein said catalyst enhancer is molybdenum..]. .[.3. The catalyst of claim 1 wherein said catalyst enhancer is ruthenium..]. .[.4. The catalyst of claim 1 wherein said catalyst enhancer is tantalum..]. .[.5. The catalyst of claim 1 wherein said catalyst enhancer is titanium..]. .[.6. The catalyst of claim 2 wherein x is between about 0.82 and about 0.90..]. .[.7. The catalyst of claim 3 wherein x is between about 0.90 and about 0.95..]. .[.8. The catalyst of claim 1 wherein said substrate is a perforated metal..]. .[.9. The catalyst of claim 8 wherein said substrate is expanded mesh..]. .[.10. The catalyst of claim 9 wherein said substrate is a metallic screen..]. .Iadd.11. A monolithic catalyst comprised of a metallic substrate with an integral Raney metal exterior surface, said surface being predominantly derived from an adherent Ni_(x) M_(1-x) Al₃ Beta structured crystalline precursory layer, where said layer is integral with and derived from said substrate, M is a catalytic enhancer selected from the group consisting of ruthenium and mixtures thereof with molybdenum, titanium, and tantalum, and where x, the weight fraction of nickel in the combined weight of Ni and M, is within the range of from about 0.80 to about 0.95..Iaddend. .Iadd.12. The catalyst of claim 11 wherein said catalyst enhancer is ruthenium..Iaddend. .Iadd.13. The catalyst of claim 12 wherein x is between about 0.90 and 0.95..Iaddend. .Iadd.14. The catalyst of claim 11 wherein said substrate is a perforated metal..Iaddend. .Iadd.15. The catalyst of claim 11 wherein said substrate is expanded mesh..Iaddend. .Iadd.16. The catalyst of claim 11 wherein said substrate is a metallic screen..Iaddend. .Iadd.17. A monolithic catalyst comprised of a metallic substrate with an integral Raney metal exterior surface, said surface being predominantly derived from an adherent Ni_(x) M_(1-x) Al₃ Beta structured crystalline precursory layer, where said layer is integral with and derived from said substrate, M is a catalytic enhancer selected from the group consisting of titanium and mixtures thereof with molybdenum, tantalum, and ruthenium, and where x, the weight fraction of nickel in the combined weight of Ni and M, is within the range of from about 0.80 to about 0.95..Iaddend. .Iadd.18. The catalyst of claim 17 wherein said catalyst enhancer is titanium..Iaddend. .Iadd.19. The catalyst of claim 18 wherein x is between about 0.90 and about 0.95..Iaddend. .Iadd.20. The catalyst of claim 17 wherein said substrate is a perforated metal..Iaddend. .Iadd.21. The catalyst of claim 17 wherein said substrate is expanded mesh..Iaddend. .Iadd.22. The catalyst of claim 17 wherein said substrate is a metallic screen..Iaddend. .Iadd.23. A monolithic catalyst comprised of a metallic substrate with an integral Raney metal exterior surface, said surface being predominantly derived from an adherent Ni_(x) M_(1-x) Al₃ Beta structured crystalline precursory layer, where said layer is integral with and derived from said substrate, M is a catalytic enhancer selected from the group consisting of tantalum and mixtures thereof with molybdenum, titanium, and ruthenium, and where x, the weight fraction of nickel in the combined weight of Ni and M, is within the range of from about 0.80 to about 0.95..Iaddend. .Iadd.24. The catalyst of claim 23 wherein said catalyst enhancer is tantalum..Iaddend. .Iadd.25. The catalyst of claim 24 wherein x is between a out 0.85 and about 0.90..Iaddend. .Iadd.26. The catalyst of claim 23 wherein said substrate is a perforated metal..Iaddend. .Iadd.27. The catalyst of claim 23 wherein said substrate is expanded mesh..Iaddend. .Iadd.28. The catalyst of claim 23 wherein said substrate is a metallic screen..Iaddend. 